The present invention relates generally to vehicular imaging systems and, more particularly, to a plastic lens or optical system which provides a wide angle field of view to an imaging device of a vehicular vision system.
Various vision systems have been proposed to enhance the view of a driver or operator of a vehicle. More particularly, vehicle vision systems, such as rear-view systems, are desired to provide an operator of a vehicle with wide angle scenic information of an area around the vehicle, such as directly rearward of the vehicle, when the vehicle is traveling in reverse. Neither interior rear-view mirrors nor side exterior mirrors allow for visibility of the area immediately rearward of the vehicle""s bumper, which is the information most critical to the vehicle operator when backing up. Therefore, various camera-based rearview vision systems have been proposed to provide visibility of this blind spot.
An example of such a proposed system includes a camera with a conventional, standard lens which is located on the rearward portion of the vehicle to provide a view of the area behind the vehicle. However, a standard lens fails to capture a wide angle view of the area, thus failing to provide the vehicle operator with an image of the entire critical area directly rearward of the vehicle.
In order to provide a wider angle view of the rearward area, a wide angle lens system may be used with the camera to capture the critical area. However, because the wide angle lens elements are typically precision optics, not only is the initial cost to manufacture and implement such a lens very high, but so is the cost to replace the lens, should it be damaged or broken on the vehicle in the vulnerable area in which it is typically located.
Another difficulty with the proposed multi-element glass lens and camera systems is that they are difficult to package within the small area available at the rearward portion of the vehicle. Such a system may comprise ten or more precision optic lens elements and is thus assembled as a long, horizontally oriented cylindrical column, which is then positioned within the trunk lid or a rear panel of the vehicle. This results in the camera system protruding substantially forwardly into the trunk space. Generally, it is desirable to minimize intrusion into the trunk space, such that the overall trunk space is maximized. This is desirable not only because trunk space is considered valuable to consumers, but also because consumers tend to over-pack their trunk spaces, and then force the trunk lid closed, which may result in damage to any components trapped between the packed items and the trunk lid. This is an even greater concern with the proposed multi-element glass lens systems, since the many optic elements may be fragile and thus prone to breaking. In a van, pick-up truck or the like, the long, cylindrical column of such a camera system would extend forward into an open space, and be more prone to damage.
The present invention provides a lens system which is adapted to provide a moderate to wide angle field of view for a vehicular imaging system, such as a vehicular video camera system or the like. More specifically, the lens system is adapted to provide a moderate to wide angle field of view of an area forwardly, rearwardly, adjacently, exteriorly and/or interiorly of a vehicle or a compartment of the vehicle. The lens system comprises a plurality of plastic optical elements consisting of at least two plastic optic elements, but no more than four plastic optic elements and, thus, is smaller and less expensive to manufacture then the multi-element precision optic lenses of the prior art.
According to one aspect of the present invention, an optical system for use with an imaging system of a vehicle includes a plurality of optical elements. The plurality of optical elements comprises less than five optical elements. Each of the plurality of optical elements comprises a plastic material. At least two of the optical elements include a diffractive element. The optical system provides a field of view of at least approximately 100 degrees to an imaging plane.
Preferably, one surface of two of said plurality of optical elements includes a diffractive element. Preferably, a surface of each of a pair of adjacent optical elements includes the diffractive elements. The diffractive elements are preferably at the surfaces of the pair of optical elements which face toward the scene being focused by the optical system. Preferably, the outer optical element has a clear aperture diameter of less than approximately 15 mm.
Optionally, the optical system provides the field of view to a sensor of an imaging system positioned at the image plane. The sensor is operable to receive the field of view from the optical system. The optical system may be implemented with at least one of a vehicular vision system for providing scenic information of an area exteriorly of a vehicle to an occupant of the vehicle, a rain sensor, a headlamp control, a backup camera, a stereo imaging system, a lane change aid camera for monitoring a side lane of the vehicle, a blind spot monitoring sensor for monitoring a blind spot at a side lane adjacent to the side of the vehicle, a forward facing lane marker detection system for monitoring or detecting the lane markers on a road to assist in keeping the vehicle traveling within the lane, and an interior monitoring system for monitoring an interior compartment or cabin of the vehicle.
In one form, the plurality of optical elements comprises an outer optical element, an inner optical element and first and second intermediate optical elements positioned between said outer and inner optical elements. The inner optical element is positioned toward the imaging plane and the outer optical element is positioned toward the scene being focused by the optical system.
According to another aspect of the present invention, an optical system for use with an imaging system of a vehicle includes a plurality of optical elements comprising an outer optical element, an inner optical element and first and second intermediate optical elements positioned between the outer and inner optical elements. The outer optical element is positioned toward a scene or targeted area being focused by the optical system. The first intermediate optical element is positioned between the outer optical element and the second intermediate optical element, while the second intermediate optical element is positioned between the first intermediate optical element and the inner optical element. The plurality of optical elements comprise less than five optical elements. Each of the plurality of optical elements comprises a plastic material. At least two of the plurality of optical elements have a diffractive element formed at a surface thereof. The optical system provides a field of view of at least approximately 100 degrees to an image plane at the inner optical element.
Preferably, the outer optical element comprises a clear aperture diameter of less than approximately 15 mm. Preferably, the optical system includes an aperture stop positioned between the second intermediate optical element and the inner optical element.
In one form, a diffractive element is formed at a surface of the second intermediate optical element and at a surface of the inner optical element. The diffractive elements are preferably formed on surfaces of the second intermediate optical element and the inner optical element facing toward the scene or targeted area that is being focused by the optical system.
Therefore, the present invention provides a lens system which includes all plastic optics or elements with two diffractive elements or surfaces. The present invention provides a wide angle focusing lens system which includes only four optics or elements, rather than the six to ten glass element lenses of conventional lens systems. By using only plastic elements, large scale fabrication is quicker and less expensive than fabrication of glass lenses. Additionally, the use of plastic optical elements provides for easy, economical addition of mounting features to the optics or the lens system to fit the particular application for the lens system. Also, by providing a lens system having only four optics, the lens system of the present invention may be more compact than lenses of the prior art.
These and other objects, advantages, purposes and features of this invention will become apparent upon review of the following specification in conjunction with the drawings.